CHICAGO — Protesters gathering in Chicago for the NATO summit geared up Sunday for the largest demonstration of the weekend, as thousands are expected to march from a downtown park to the lakeside convention center where President Barack Obama and other world leaders were meeting.

Hours before the main demonstration was set to start, protesters — including peace activists, war veterans and those more focused on the economy — began arriving at Grant Park, holding signs denouncing NATO, including ones that read: "War(equals)Debt" and "NATO, Go Home."

Organizers of Sunday's rally had initially predicted tens of thousands of protesters this weekend. But that was when the G-8 summit also was scheduled to be in Chicago. Earlier this year, Obama moved the Group of 8 economic meeting to Camp David, the secluded retreat in rural Maryland.

Chicago kept the NATO summit, which will focus on the war in Afghanistan and other international security matters, but not the economy. That left activists with the challenge of persuading groups as diverse as teachers, nurses and union laborers to show up for the Chicago protests even though the summit's main focus doesn't align with their most heart-felt issues.

Sunday's protest followed several, smaller demonstrations the previous two days including one peaceful march to the home of Mayor Rahm Emanuel, Obama's former chief of staff, on Saturday. But a march later that evening involving hundreds of demonstrators stretched for hours as protesters zigzagged back and forth through downtown, some decrying terrorism-related charges leveled against three young men earlier in the day.